The present invention relates to a method and apparatus for quickly and consistently reinitializing a tape drive after a loss of power to the tape drive.
Single reel tape cartridges are used to transport and store tape for reel-to-reel tape drives. A single reel tape cartridge is inserted into a tape drive and a mechanism is used to load the end of the tape into a take-up reel from the tape cartridge. Once the end of the tape is loaded into the take-up reel, the tape drive operates as a reel-to-reel tape drive. A motor is coupled to the takeup reel to rotate the take-up reel about the take-up reel axis and another motor is coupled to the single reel tape cartridge to rotate the reel of the tape cartridge about its axis.
The tape drive mechanism attaches to a tape leader pin, located at the end of the tape contained in the single reel tape cartridge. The hub filler uses a slot in the hub filler for receiving the tape leader pin. The hub filler is coupled to a guide arm that drives the hub filler between the single reel tape cartridge and the take-up reel. An example of a mechanism for driving the hub filler between the tape cartridge and the take-up reel is disclosed in U.S. Pat. No. 6,034,839.
FIG. 1 is a view of the tape drive mechanism disclosed in U.S. Pat. No. 6,034,839. The hub filler 300 enters into the cartridge 210 and attaches to the end of the tape. The hub filler 300 then moves along a guide rail 247, driven by the guide arm 250. Typically, the hub filler 300 attaches to the end of a tape in the tape cartridge 210 and the guide arm 250 moves the hub filler 300 along the guide rail 247, trailing the tape across the read/write head 222 and into the take-up reel 242. The hub filler 300 enters the take-up reel 242 through a channel 244 and into the hub 245 of the take-up reel 242.
FIG. 2 is a top view of the tape drive mechanism, depicting the hub filler 300 in the take-up reel 242 with the tape 216 attached. The single reel tape cartridge 210 is positioned in the tape drive. The tape 216 is wound on a reel inside the cartridge 210. The end of the tape 216 is attached to a leader pin 214. The hub filler 300 has transported the end of the tape 216 along the guide rail 247, driven by the guide arm 250, from the cartridge 210 to the takeup reel 242. During this transportation hub filler 300 pivots on axle 252 and is held to the guide rail 247 by pressure from a spring. The hub filler 300 also includes a catcher that attaches to the leader pin 214 when entering the cartridge 210. The tape 216 is passed across the read/write head 222 and the end of the tape 216 is secured to the take-up reel 242. The tape drive is then operated by rotation of the take-up reel 242 and the single reel of the cartridge 210 about their respective axes to move the tape 216 across the read/write head 222. Motors are used to rotate the take-up reel 242 and the single reel of the cartridge 210, controlling the speed of the tape 216 as it moves across the read/write head 222. The hub filler 300 pivots on an axle 252 that is coupled to the guide arm 250. This pivoting is necessary for the hub filler 300 to be guided on the guide rail 247 into the take-up reel 242. Once the hub filler 300 is in the take-up reel 242, with the tape 216 attached, the take-up reel 242 rotates to thereby unload the tape from the cartridge 210. The hub filler 300 rotates with the take-up reel 242 on the axle 252.
There are some concerns regarding the conventional tape drive described above. During the sequence of operations of a conventional tape drive mechanism there is a possibility of a power loss. When power is eventually restored to the tape drive, it is difficult for a controller that controls the mechanical operation of the conventional tape drive to determine what operation in the sequence of operations the conventional tape drive was performing at the time of power loss. In other words, the controller does not know, after the restoration of power, how to continue operation of the tape drive. When the conventional tape drive inevitably continues operation after restoration of power, there is a likelihood that the leader pin 214 will become disengaged from the hub filler 300. This problem may exist when, at the time of power loss, the hub filler 300 was in between the tape cartridge 210 and take-up reel 242. Such a circumstance will effectuate a xe2x80x9cjamxe2x80x9d in a tape drive and cause the tape drive to be temporarily inoperable. This circumstance is very inconvenient for the user of the xe2x80x9cjammedxe2x80x9d tape drive and may cause significant delays for the user.
Some conventional tape drives include sensors that sense the position of the mechanical parts of the tape drive mechanism after recovery of power. However, these sensing arrangements can be somewhat inaccurate and this inaccuracy can cause the tape drive mechanism to be xe2x80x9cjammedxe2x80x9d, as discussed above. Further, this sensing of the position of the mechanical parts after a power recovery often does not provide enough information to determine the direction the mechanical parts were moving when the power loss occurred. In other words, the conventional tape drive mechanism cannot consistently resume operation during reinitialization from where the tape drive mechanism was operating prior to power loss. This may cause an undesirable delay during reinitialization. Further, the hardware necessary for sensing the position of mechanical parts of the conventional tape drive takes up valuable space in the tape drive, which is undesirable in compact tape drives.
There is a need for a tape drive that can consistently resume operation during reinitialization after a power loss, with minimum time delay. There is also a need for a tape drive mechanism that can consistently resume operation during reinitialization after a power loss, but consumes minimal space.
These and other needs are met by embodiments of the present invention, which provide a method and apparatus of utilizing a non-volatile memory that stores the functional state of a tape drive throughout the operation thereof. Particularly, in embodiments of the present invention, the tape drive mechanism is arranged to store in the non-violatile memory the last instruction issued from a controller to the tape drive mechanism. This last issued instruction is further stored in relation to the sequence of instructions that the tape drive mechanism is performing at time of storage. Accordingly, if a power loss occurs during the operation of the tape drive mechanism according to an issued instruction, the tape drive is arranged to read the functional state of the tape drive mechanism from the non-volatile memory during reinitialization.
The present invention has the advantage of fast reinitializing after power loss. This is possible, since the last issued instruction in relation to the sequence of instructions that the tape drive mechanism was performing at the time of power loss is stored in the non-volatile memory. Accordingly, after a power loss, the tape drive mechanism can resume operation without significant delay during reinitialization. Hence, it is unnecessary for the tape drive to sense or attempt to determine where in the sequence of instructions the tape drive was at the time of power loss, based on the position of the mechanical parts of the tape drive mechanism.
Another advantage of the present invention over a conventional tape drive is that mechanical failure or xe2x80x9cjammingxe2x80x9d is less likely to occur. In embodiments of the present invention, the tape drive can resume operation at the same instruction in the sequence of instructions during reinitialization with a significant reduction, in comparison to a conventional tape drive, in the probability of mechanical failure or xe2x80x9cjammingxe2x80x9d. For instance, in a conventional tape drive, if a hub filler is transporting an end of tape with a leader pin attached, it is possible for the leader pin to detach from the hub filler during reinitialization. This causes the tape to be xe2x80x9cjammedxe2x80x9d in the tape drive. This can occur for a variety of reasons. One reason is that during reinitialization of a conventional tape drive, it is necessary to perform several mechanical operations to sense the position of the hub filler. Accordingly, during these mechanical operations, the leader pin can be inadvertently detached from the hub filler. Another reason is that during reinitialization, it may not be possible through the use of sensors to determine where in the sequence of instruction the conventional tape drive mechanism was operating during the power loss. More particularly, the conventional tape drive mechanism may not be able to determine whether the tape was being loaded or unloaded at time of power loss. Accordingly, the tape drive of the present invention alleviates this disadvantage by storing the functional state in relation to the sequence of instruction the tape drive mechanism was performing at time of power loss, so that during reinitialization the tape drive mechanism can efficiently and consistently resume operation.
The foregoing and other features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the present invention, taken in conjunction with the accompanying drawings.